In recent years, an electric automobile or a hybrid electric automobile (hereinafter, simply called “electric automobile”) mounted with a battery for driving a motor has been rapidly developed. The battery mounted on the electric automobile is required as a matter of course to have reduced weight in order to improve drivability and mileage per charge. In order to reduce battery weight, a film covered battery has been developed using a laminate material formed into a thin film by laminating a metal layer, like aluminum, and a thermal-melt resin layer through an adhesive layer on the covering body. The laminate material generally has a structure, in which both surfaces of the thin metal layer, like aluminum, are covered with thin resin layers, and is resistant to acid and alkali and is lightweight and flexible.
Generally, the property of the battery is influenced by the expansion and contraction of the active materials of the cathode and anode during charge/discharge. Therefore, conventionally, the battery is housed in a metal container in order to prevent deformation.
On the other hand, in the film covered batteries, laminate film used as the covering is not able to suppress expansion of the battery. Therefore, batteries that are covered with laminate films are configured such that a proper load is placed on the battery in order to suppress expansion of the electrodes. As the method of suppressing the expansion of the battery, Japanese Patent Laid-Open No. 10-012278 discloses the technique in which an electric power generating element including a group of laminated electrodes is stored in a holding member having a U-shape in a cross section and having a plurality of projections on two inner surfaces that are face each other.
Also, when the film covered battery is mounted on an electric automobile, it is necessary to address the problems concerning protection from impact and or using as an assembled battery etc. As a method of protecting the cell element from external impact, Japanese Patent Laid-Open No. 2000-357493 discloses a battery frame in which the battery elements are housed in a box-shaped frame.